Rapid fabrication environments use mechanical systems to construct tangible objects from digital model representations. Rapid fabrication may also be referred to as rapid prototyping or as three-dimensional printing. The digital model representations are usually stored as computer files, e.g., as computer-aided design (CAD) files or STL files.
Two example systems for rapid fabrication are stereolithography machines and fused deposition machines, which are both forms of additive manufacturing. In stereolithography, a thin layer of a photo-reactive resin is cured using a laser, whereas in fused deposition, small amounts of a material are deposited by an extruder. In general, rapid fabrication builds an object out of a single source material. For example, in stereolithography, the resulting object is made entirely from the photo-reactive resin. See, for example, U.S. Pat. No. 5,556,590 issued in 1996 to Charles W. Hull, titled “Apparatus for production of three-dimensional objects by stereolithography.” In fused deposition systems, the resulting object is made entirely from the deposited material. See, for example, U.S. Pat. No. 5,121,329 issued in 1992 to S. Scott Crump, titled “Apparatus and method for creating three-dimensional objects.”